1. Field of the Invention
This invention relates to a method for the operation of a fuel system for an internal combustion engine that is operated with fuel gas, the fuel system having at least one electrically actuated shutoff valve and at least one electrically operated heating device for the fuel gas.
2. Description of the Currently Available Technology
Internal combustion engines powered by fuel gas are frequently used in industrial trucks, such as fork-lift trucks, as well as in passenger vehicles. The fuel gas used for this application is typically referred to as liquid petroleum gas or LPG and consists primarily of propane and/or butane.
The fuel system of an internal combustion engine of this type comprises a fuel container in the form of a high-pressure gas bottle or a high-pressure tank, an evaporator, and a shutoff valve that is located upstream of the evaporator. In the evaporator, the fuel gas, which is typically stored in the form of a liquid, is depressurized and thereby transformed into a gas, wherein thermal energy is added to the fuel gas. After a relatively long period of operation of the internal combustion engine, this heat is generally derived from the coolant of the internal combustion engine. The fuel system also has at least one electrical heating element to provide at least approximately total evaporation of the fuel gas during cold starts of the internal combustion engine. The evaporator can also include a pressure regulator so that the fuel gas will be available at the output of the evaporator in the form of a gas at a defined pressure. An additional component of the fuel system located downstream of the evaporator is a mixer, the function of which corresponds to the carburetor or fuel injection system of a gasoline engine.
It is an object of the invention to provide a method for the operation of a fuel system which securely prevents the accumulation of critical amounts of liquid fuel gas downstream of the evaporator under substantially all operating conditions.